Bag closure and method of sealing a bag



June 6, 1967 P. P. SPOLSINO 3,323,272

BAG CLOSURE AND METHOD OF SEALING A BAG Filed Dec. 25, 1964 5 Sheets-Sheet l June 6, 1967 P. PASPOLSINO BAG CLOSURE AND METHOD OF SEALING A BAG Filed Dec. 23, 1964 A 3 Sheets-Sheet 2 m m w o W m 3 .l. 2. 3/ V O "w a. W 4 \3 thunk 3 E AE Q o u im E E 1 7 FIG. 2

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June 6, 1967 P. P. SPOLSINO AG CLOSURE AND METHOD OF SEALING A BAG 5 Sheets-Sheet 3 Filed Dec. 23, 1964 United States Patent 3,323,272 BAG CLUSURE AND METHOD OF SEALHNG A BAG Peter Paul Spolsino, Revere, Mass, assignor to W. R. Grace it: (30., Cambridge, Mass., a corporation of Connecticut Filed Dec. 23, 1964, der. No. 420,720 3 Claims. ((11. 53-14) This is a continuation-impart of my copending application, Ser. No. 312,696, filed Sept. 30, 1963, now US. Patent No. 3,187,481, which was in turn a continuationin-part of Ser. No. 163,168, now 11.8. Patent No. 3,111,- 794.

This invention relates to a sealed bag sealing. In one aspect the invention relates to a method for sealing the gathered end of a thermoplastic bag so as to obtain an airtight seal.

A common method of sealing the open end of thermoplastic bags requires that opposite sides of the open mouth be brought together and that sufficient heat be applied to the thermosplastic material to fuse the two sides together. This necessarily results in a rather wide closure extending the width of the package which, while suitable for packaging some products, is equally unsuitable for others. For example, when packaging whole poultry or primal meat cuts, it is preferred that the bag, including the sealed area, closely conform to the product. Conventional heat sealing, therefore, produces seals that lie some distance from the end of the product and are relatively straight, loose fitting seals.

Another method of closing bags (and one that permits the sealed area to more closely conform to the product) involves the application of a deformable metal band about the gathered end of the bag. The clip can be applied to the gathered end of the bag in close proximity to the bagged product. With the development of clip applying devices and suitable clips, it is now possible with this method to quickly obtain reliable seals. Several problems exist in connection with clip sealing, the most serious of which is the difiiculty in obtaining an air tight closure. The gathered neck of the bag about which the clip is applied has a myriad of channels created by the folding of the bag through which air can pass into the interior of the bag. To close off these channels, it is necessary to apply the clips tightly around the gathered neck of the bag. Because the bags of thermoplastic material are relatively fragile, the use of sufficient pressure to close the air passages is likely to cause the clip to tear into the bagdestroying the integrity of the closure. The problem is even more serious with large bags, since correspondingly greater pressures must be applied to seal the bag.

While it would theoretically be possible to heat fuse the gathered neck of a thermoplastic bag, this is not practical, since the fused material must be held under restraint or otherwise supported while the material is cooling and solidifying. A not inconsiderable length of time must elapse before the seal acquires any strength. The time required to cool the fused thick mass of material to a point where the heat seal will become self-supporting has proven to be of such long duration that it has not been considered economically practical to seal bags in this manner.

In my patent, US. 3,111,794, I have proposed a method and device for producing an improved bag closure. By this method a metal clip is crimped around a twisted or gathered end of a bag and then a hot knife severs the end of the bag at a short distance from the clip. The side of the hot knife is then pressed against the severed end of the bag so as to fuse the exposed end. In my copending application, S.N. 312,696, now Patent No. 3,187,481, -a device is disclosed whereby a length of masking tape or the like is used in lieu of the metal clip. Although both of these techniques produce generally satisfactory closures, there is some difiiculty in obtaining an air-tight seal. Since the end portion of the bag extending beyond the clip or tape tends to flare outwardly when the hot knife surface is pressed against the exposed film, it is difficult to completely fuse the end portion. This leaves tiny capillaries through the gathered end and thus permitting a gradual loss of vacuum in the bag over prolonged periods of time.

It is an object of the present invention to provide a method for obtaining an air tight seal on thermoplastic bags of any size, which seal will be relatively small and conform to the product. It is a further object to provide a sealed thermoplastic bag having an air tight seal.

Other objects and advantages of the present invention will become apparent from the following detailed description of the invention taken in conjunction with the accompanying drawings wherein:

FIGURE 1 is a perspective view of the apparatus of this invention.

FIGURE 2 is a front elevational view of the apparatus of FIGURE 1.

FIGURE 3 is a top plan View of the apparatus.

FIGURE 4 is -a section taken on about line 4 4 of FIGURE 3, certain elements being broken away for bet ter clarity.

FIGURE 5 is a perspective view schematically illustrating certain steps in the operation of the apparatus, and

FIGURE 6 is a perspective view of the final seal.

It has now been found that by employing a tape and by severing the gathered end of the bag and the tape simultaneously that a clean, smooth end is presented to the hot knife surface which will not flare outwardly. This results in complete fusion of the severed end of the bag thus eliminating leakers.

Any suitable apparatus may be employed for gathering (or twisting) the end of the bag, severing the tape and gathered end and fusing the severed end. A particularly suitable device is shown in my copending application, S.N. 312,696, now US. Patent No. 3,187,481, issued June 18, 1965.

This device comprises, in general, a product support unit It a tape dispensing and clamping unit 11, a bag cutoff and sealing unit 12, an evacuating unit 13 and a tape cut-off unit 16. All units are placed upon a work surface 14, e.g., a platform or floor.

The product support unit 10 is illustrated as a stationary table 15. If desired the support unit could comprise a conveyor which delivers the bagged product (e.g., whole ham 17 in thermoplastic bag 18) from a product bagging station (not shown).

The tape dispensing and clamping unit and the bag cut-off and sealing unit are both mounted on a common carriage 19. This carriage rides on the work surface 14 and is reciprocally movable thereon. In the illustrated apparatus the carriage 19 is mounted on a plurality of wheels 20 and is moved to and fro by a carriage mover comprising an air operated cylinder 21, the piston rod 22 of which is secured to the back plate 23 of the carriage.

The tape dispensing and clamping unit 11 is fixedly secured on the top of movable carriage 19 adjacent the side closest to the product support table. The detailed construction of the tape dispenser is best seen in FIGURES 1 and 4, wherein it is seen that the unit comprises a supply roll 24 of pressure sensitive adhesive tape mounted in a conventional dispenser housing (not shown). The tape 26 is drawn from the supply roll with the adhesive side exposed. The tape is fed under the guide rolls 27, 28 mounted on elongated arm 29 which extends beyond the front side 30 of carriage 19. The face 31 of the extended end of arm 29 is grooved to form a saddle 32 therein.

The clamping device 50 in the illustrated apparatus is mounted on the forward face of carriage 19 directly below extended arm 29 of the tape dispenser. A U-shaped yoke 51 which is bolted or otherwise secured to the carriage face 30 supports the clamp. A pinion gear 52 is held between the legs of the yoke 51 by a shaft 53, the respective ends of which extend through the legs of the yoke a sort distance. Clamp arms 54 and 55 are secured to the ends of the shaft 53. The gear and clamp arms are fixedly secured to the shaft so that rotation of the gear rotates the shaft, which in turn will move the clamp arms. The clamp arms are shaped in a suitable manner so that the outer free ends thereof will generally mate with the saddle 32 when the clamp is moved to operative position. Freely rotatable rollers 57 and 58 are mounted between the free ends of the clamp arms in suitable manner.

The clamp is moved into operative position by means of a driven rack 60 which co-operates with the pinion gear 52. The rack is moved to and fro by an air cylinder 62, the piston of which is fixed to or integral with the rack 60.

The cut-off and fuse sealing unit 12 is mounted slightly behind the tape dispensing unit. In addition to moving to and fro together with the tape dispensing unit, the cutoff unit is mounted for movement toward and away from and in a direction generally perpendicular to the elongated arm 29 of the tape dispenser. In the illustrated embodiment this is accomplished by mounting the cut-off unit 12 on a second movable carriage 33 which is independently reciproc-able on top of movable carriage 19. Carriage 33 is made movable by mounting it on a plurality of wheels 34. Reciprocal movement is obtained from a carriage mover comprising air cylinder 35 and piston rod 36 secured to the rear side of carriage 33.

Near the forward top edge of the carriage 33 there are two knife guide rods 63. Knife bar 64 is bored out and mounted to ride up and down on the guide rods. A knife air cyliner 65 is mounted on support plate 66 between the rods. The plate 66 is fixedly secured to the top of carriage 33 and is maintained in generally fixed vertical position by struts 70. The piston 67 of the cylinder is secured to the top of knife bar 64. The knife bar extends towards the forward side of the apparatus. The knife blade, per se, is secured to the extended end of the bar so that it is generally in the same vertical plane as the saddle groove 32 in the tape dispensing unit. The knife is designated 67 in the drawings.

The blade is heated in known manner by inserting cartridge heaters (not shown) therein. The heaters are connected to a suitable electric power source (not shown) via flexible electric power line 68 (shown in FIGURE 5). The knife blade is maintained hot at all times during operation of the machine. Suitable temperatures are from about 450 to 600 Fahrenheit, depending primarily upon the particular thermoplastic from which the bag 18 is I made.

The evacuating unit 13 is constructed in known manner. It comprises, in general, a vacuum nozzle 37 fixedly mounted on the end of rotatable conduit 38 which in turn communicates with vacuum chamber 39. Sub-atmospheric pressure created in the chamber 39 via flexible hose 40 connected to a suitable evacuation device such as a vacuum pump (not shown). Conduit 38 (and thus nozzle 37) are rotated by connection to the motor 41 via a gear reducer 42 and clutch assembly 43.

The tape cut-off unit includes knife 80 which is secured to the end of piston 81 of air cylinder 75. Ordinarily this knife is in retracted position and is enclosed in a shield housing (not shown) for safety reasons. The air cylinder 75 which drives the knife is mounted on carriage 19 by a suitable support bracket 77. This bracket positions the tape cut-off knife several inches in front of the saddle groove 32 and in line with the extended arm 29 of the tape dispenser. The cutting edge 84 of the knife 80 is 4 serrated to aid in making the transverse cut in the tape 26.

The actuation of the evacuating unit 13, the carriage 19, the cut-off unit 12, the carriage 33', and the tape cutoff knife 80 is performed in a timed sequence via conventional timing circuits and switches. The timing mechanisms and their operation are so well known in the art that detailed description thereof is not deemed necessary for purposes of understanding the present invention.

In operation, product (such as whole ham 17, or a turkey, chicken, primal meat cut, etc.) in a bag 18 of thermoplastic film (such as Saran, polyethylene, polypropylene, etc.) is brought to a rest position on support unit 10. The open neck of the bag is drawn over the vacuum nozzle 37 and held around the conduit 38. The vacuum pump (not shown) is turned on and operates until the bag is substantially evacuated.

The timing device is then activated. Its first operation is activation of the drive motor 41 to twist the nozzle 37 and make a twisted rope of the extended bag neck. Next the timer actuates air cylinder 21, moving carriage 19 forward until the twist bag neck rests in saddle 32 in the arm of the tape dispenser. Prior to this, tape is drawn from the supply roll for a distance suflicient to leave at least a short length draped over the end of arm 29 and thus hanging in front of the saddle.

The movement of the twisted bag neck into the saddle pushes the end of the tape into the saddle. The clamp unit is simultaneously actuated and pushes the bag neck and tape firmly into the saddle.

At this point the timer again actuates the motor 41 so that the bag neck is further twisted. During this second twist the pressure exerted by clamp 50 is sufficient to make the tape adhere to the bag neck. Continued twisting causes further tape to be drawn from the supply roll and drawn tightly about the neck (to form an encircling sleeve 45).

Twisting of the end of the neck on the vacuum nozzle causes a shortening of the neck which draws the bag toward the fixed end of the bag. Since the tape is being continuously dispensed, a portion of the tape sleeve extends beyond the edges of the clamp 50 so as to be directly under the knife 67.

The motor 41 is deactivated and air cylinder is activated, driving the heated cut-off knife 67 down and through the tape encircling the bag neck and the twisted bag. As soon as the cut is complete, the timer actuates air cylinder 35, so that the carriage 33 moves toward the tape dispenser. The tape and bag neck are cut so as to leave no exposed edge portions of film.

Movement of the carriage 33 axially compresses the end of the bag between the hot knife 67 and the tape sleeve 45 (see FIGURE 5). In a very short time (e.g. 3 to 4 seconds for Saran films) the tape neck is fused into a solid mass. The clamp 50 holds the tape-encircled neck portion in place so that the end of the neck cannot move away from the hot knife. As shown in FIGURE 6 this produces a smooth fused closure.

The carriage 33 is then withdrawn and the cut-off knife is retracted. At the same time carriage 19 is withdrawn to its rest position, and the clamp 56 is returned to its normal position i.e., open. When carriage 19 reaches its rearward rest position air cylinder is actuated, driving tape cut-01f knife downward to sever the tape an inch or so in front of the face 31 of the arm 29. The severed tape drapes over the face 31 is front of saddle groove 32 in readiness for the next cycle.

The invention has been described with emphasis on the employment of particular apparatus. The invention is not so limited. Any suitable apparatus may be used which gathers or twists the end of a bag containing product, encircling a portion of the gathered or twisted end with a tape so as to restrain the end portion, cutting through the tape and bag and fusing the severed bag end. Any severing means may be employed including a knife, hot wire, radiant heating or the like. Any suitable fusing means may be employed including a hot flat surface, radiant heating means or the like. The term tape as employed herein includes any flexible self adhering strip or band of material which may be readily cut. A presently preferred material i masking tape.

What is claimed is: 1. A method for sealing the open end of a thermoplastic bag which comprises:

(a) gathering the open end of the bag to form an elongated neck, (=b) tightly encircling a portion of said neck with a pressure sensitive adhesive tape to form a tape sleeve, (0) transversely severing the bag neck through the said sleeve, thus leaving the sleeve at the extremity of the neck, ((1) heating the exposed severed bag neck above its fusion temperature and (e) compressing the heated portion toward the sleeve to form a compact fused mass. 2. A method for sealing the open end of a thermoplastic bag which comprises:

(a) twisting the open end of the bag to form an elongated neck, (b) tightly encircling a portion of said neck with a self adhering tape to form a tape sleeve, (c) severing said bag neck through said tape, (d) heating the exposed severed bag neck above its fusion temperature and (e) compressing the heated portion toward the sleeve to form a compact fused mass.

3. A method for sealing the open end of a thermoplastic bag which comprises:

References Cited UNITED STATES PATENTS 2,088,232 7/1937 Cumming 229-62 2,783,599 3/1957 Weikert 53-30 3,011,690 12/1961 Gabuzda 229-62 3,088,255 5/1963 Greim 53-14 3,111,794 11/1963 Spolsino 53-14 3,113,408 12/1963 Kirkpatrick 53-30 TRAVIS S. MCGEHEE, Primary Examiner. FRANKLIN T. GARRETT, D. M. BOCKENEK,

Assistant Examiners. 

1. A METHOD FOR SEALING THE OPEN END OF A THERMOPLASTIC BAG WHICH COMPRISES: (A) GATHERING THE OPEN END OF THE BAG TO FORM AN ELONGATED NECK, (B) TIGHTLY ENCIRCLING A PORTION OF SAID NECK WITH A PRESSURE SENSITIVE ADHESIVE TAPE TO FORM A TAPE SLEEVE, (C) TRANSVERSELY SEVERING THE BAG NECK THROUGH THE SAID SLEEVE, THUS LEAVING THE SLEEVE AT THE EXTREMITY OF THE NECK, (D) HEATING THE EXPOSED SEVERED BAG NECK ABOVE ITS FUSION TEMPERATURE AND (E) COMPRESSING THE HEATED PORTION TOWARD THE SLEEVE TO FORM A COMPACT FUSED MASS. 